Chapter 3: System planning
Link planning
Page 3-29
Link planning
This section describes factors to be taken into account when planning links, such as range,
obstacles path loss and throughput. LINKPlanner is recommended.
LINKPlanner
The Cambium LINKPlanner software and user guide may be downloaded from the support
website (see
).
LINKPlanner imports path profiles and predicts data rates and reliability over the path. It allows
the system designer to try different antenna heights and RF power settings. It outputs an
installation report that defines the parameters to be used for configuration, alignment and
operation. Use the installation report to compare predicted and actual link performance.
Range and obstacles
Calculate the range of the link and identify any obstacles that may affect radio performance.
Perform a survey to identify all the obstructions (such as trees or buildings) in the path and to
assess the risk of interference. This information is necessary in order to achieve an accurate
link feasibility assessment.
The PTP 550 Series is designed to operate in Non-Line-of-Sight (NLoS) and Line-of-Sight (LoS)
environments. An NLOS environment is one in which there is no optical line-of-sight, that is,
there are obstructions between the antennas.
The PTP 550 Series will operate at ranges from 100 m (330 ft) to 200 km (122 miles). Operation
of the system will depend on obstacles in the path between the units. Operation at 40 km (25
miles) or above will require a near line-of-sight path. Operation at 100 m (330 ft) could be
achieved with one unit totally obscured from the other unit, but with the penalty of transmitting
at higher power in a non-optimal direction, thereby increasing interference in the band.
Path loss
Path loss is the amount of attenuation the radio signal undergoes between the two ends of the
link. The path loss is the sum of the attenuation of the path if there were no obstacles in the
way (Free Space Path Loss), the attenuation caused by obstacles (Excess Path Loss) and a
margin to allow for possible fading of the radio signal (Fade Margin). The following calculation
needs to be performed to judge whether a particular link can be installed:
capability
seasonal
fade
excess
space
free
L
L
L
L
L
<
+
+
+
_
Where:
Is:
space
free
L
_
Free Space Path Loss (dB)
excess
L
Excess Path Loss (dB)
fade
L
Fade Margin Required (dB)
